Megapixels - Image Quality

I need to get a digital SLR camera for photography school. Primarily, standard 8X10 prints will required
from the assignments that I will be turning in from the work done on this camera. Now I can afford a
camera between 6-10 megapixels. Obviously, I want the work I turn in to look as nice as possible.

My question is, in an 8X10 print, can one tell the difference between 6 vs. 10 MP (assuming of course
everything else remains the same)?

without interpolation. The rule of thumb is a digital print on
close inspection will yield visibly best results at 300-360 pixels
per inch. (I'm handwaving here).

I think you will be floating around the undetectable range in image capture quality - I
suspect that printer choice and how the image is prepped (sharpening in particular) will
have a greater effect on the final appearance of the print?

In fine mapping with microfonts from hell ; or a micro cross hatch a 600 ppi image one the print might be required. For a poster many feet away a 50 ppi image is often overkill. For a billboard a 4 to 6 ppi image is often totally ok; even overkill if an interstate one seen 100's of feet away. The 250 number to 350 numbers for a print say 8x10 are usually ok. Unless the purpose of the image is know; whats it made up of; and the viewing distance; you will get alot of answers. In 11x17" maps we print with dinky street names we often use 400 ppi; so street names are clear.

At 8x10 you shouldn't see any difference, but all else being equal buy as many megapixels as you can afford. There may be a shot made with the camera some day that you're want to blow up to 11x14 or 16x20 or even larger, so don't limit yourself by trying to save $100 if you don't have to. To get 300 ppi on and 8x10 you mathematically need 7.1 megapixels, but the correlation of megapixels to print size is fuzzy math. Yo may be able to get by with fewer than a certain number, but there's no such thing as too many. (Despite the extra cost and need for larger memory cards and a faster computer.)

10Mpix will allow you to do some (more) cropping if needed. But I do believe that the pixel rush we are having is more related to marketing than real quality of the image (6 goob Mpix is better than bad 10Mpix).

You will see a bigger difference due to a lens than due to 4MP difference on a 11x14 print. Get the cheapest 6MP camera with the best lens you can afford. Canon or Pentax probably have an edge, as Nikon doesn't have autofocus primes for D40. A second hand Canon 350 with the 50 1.8 and 10-22 zoom will set you up, just like the Pentax 10D with the 21 and 50 lenses. Less MP per sensor size equals also less noise and better dynamic range. Fuji S2, or better S3 is another excellent choice.

Among the current batch of DSLR's, all should be capable of producing excellent 8x10's. I think it will be the rare image where you can see much difference between 6 MP and 10 MP in an 8x10 inch print. In fact, at that size, I often find the differences between 4 MP and 6 MP are subtle.

(Of course, with some printers and very rare images, it is theoretically possible that you might see more resolution up to 22 MP or so--that that's under perfect conditions. "Perfect" human vision would let you see up to around 375-400 ppi at typical 8x10 viewing distances, and there are printers that can print that resolution. And to get 4 pixels worth of real resolutuion from a typical Bayer sensor, you need about 5 pixels on the sensor. 8 in x 1.25 x 380 pixels / in = 3800 pixels vertical, so a 3:2 sensor that would mean 22 MP. But this is more theory that reality!)

It really depends on a lot more things than megapixels. I work in a photo lab, and we print on
a Agfa-Geveart D-LAB.3, which prints 400 DPI.

I have had people come in and print beautiful 8x10's from a 5 mp Canon point and shoot,
and I have tried to print photos attempted in crappy lighting, ISO 1600, with the kit lens
taken with be 8 megapixel Canon SLR and had then turn out absolutely horrible.

But like others have said, any SLR on the market today can handle an 8x10. If it couldn't the
company would be out of business.